题目

下图是某家族的系谱图。现已查明II—3不携带致病基因。若III—9和III—12婚配，子女中只患甲病的概率和只患一种遗传病的概率分别是                                          （    ）        A.7/12 ，5/8                                  B.7/12, 3/8        C.7/24 ,  9/24                                 D.1/4 ,5/12He didn’t work hard, ________, he failed his exam.A．in factB．as wellC．by the wayD．as a result